<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />

    <link href="lib/twitter-bootstrap/css/bootstrap.css" rel="stylesheet" />

</head>
<body>
    <div class="container">

        <nav class="navbar navbar-expand-sm bg-dark navbar-dark">
            <div class="container-fluid">
                <a class="navbar-brand">
                    <img src="img/s_5.png" width="50" height="50" alt="Alternate Text" />
                </a>
                <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navBar">
                    <span class="navbar-toggler-icon"></span>
                </button>
                <!--5.0版本关键字：data-bs-xxx-->
                <div id="navBar" class="collapse navbar-collapse">
                    <ul class="navbar-nav">
                        <li class="nav-item"><a class="nav-link">学生列表</a></li>
                        <li class="nav-item"><a class="nav-link">添加</a></li>
                        <li class="nav-item dropdown">
                            <a class="nav-link dropdown-toggle" data-bs-toggle="dropdown">
                                下拉框
                            </a>
                            <ul class="dropdown-menu bg-light">
                                <li class="dropdown-item">王城城</li>
                                <li class="dropdown-item">王橙橙</li>
                                <li class="dropdown-item">王成成</li>
                            </ul>
                        </li>
                    </ul>
                </div>
            </div>
        </nav>
    </div>

    <script src="lib/jquery/jquery.js"></script>
    <script src="lib/twitter-bootstrap/js/bootstrap.js"></script>

</body>

</html>